Molecular Biology Answers

The recipe for PBS says to dissolve compounds in 800 ml of water, adjust the pH to 7.4, then add water up to 1 liter. The final pH should still be 7.4, because the pH of buffer solutions remains stable when they are diluted as long as the concentration of its constitutive acid and base is not too low.

Question 10: Why do you think the protocol does not say to dissolve compounds directly in 1 liter of water?

Question 9: What should be done before measuring an unknown pH of a solution using a pH meter?

Question 8: If you had the choice between a 1 liter beaker and a 1 liter graduated cylinder, which one should you use to measure volumes with maximal precision when making 1 liter of PBS?

Question 7: If you have excess reagent on the weighing boat, what should you avoid doing and why?

Question 6: What is the first thing to do after putting a weighing boat on the balance?

Question 5: As previously stated, the concentration of NaCl, KCl and Phosphate in working strength 1 x PBS is 0.137M NaCl, 0.012M Phosphate, 0.0027M KCl, pH 7.4 How do they compare to the concentrations you calculated for 10x PBS?

Question 4: Using periodic table found in your textbook, calculate (to 2 decimal places) the molecular mass for each of the compounds used to make PBS.

Create the following table and fill it in with the mass of each component required to make 1 liter of 10 x PBS (the recipe for 10x PBS is below question 2) and their final molar concentration in the buffer calculated as described above.

Compound formula Molecular mass (in g/mol) Mass of compound per liter of 10x PBS (in g) Molar concentration (in mol/l)
NaCl
KCl
Na2HPO4
KH2PO4

Question 3: Which ions are being produced by this process, assuming that each of the chemical compounds dissociate into their constituent parts once they are dissolved in water?

It is sometimes difficult to evaluate the risks posed by biotechnology because:

A. It is impossible to carry out large-scale trials for risk assessment
B. It is difficult to know how a genetically modified organism will interact with other organisms in its ecosystem and what the biological consequences will be
C. Animals cannot be used to test products that are designed for humans
D. The cost of risk assessment for most biotechnological products is too high
.Which of the following is an ethical concern related to genetically engineering human beings?

A. Increased socioeconomic problems
B. Torture of animals to reach this end
C. Potential human genetic homogeneity, leading to an increased chance of the species being wiped out
D. Increased environmental problems

A mutation within the promoter region can alter transcription of a gene. Describe how this can happen